Differences in the postexercise threshold for cutaneous active vasodilation between men and women

The purpose of this study was to evaluate the possible differences in the postexercise cutaneous vasodilatory response between men and women. Fourteen subjects (7 men and 7 women) of similar age, body composition, and fitness status remained seated resting for 15 min or cycled for 15 min at 70% of peak oxygen consumption followed by 15 min of seated recovery. Subjects then donned a liquid-conditioned suit. Mean skin temperature was clamped at approximately 34 degrees C for 15 min. Mean skin temperature was then increased at a rate of 4.3 +/- 0.8 degrees C/h while local skin temperature was clamped at 34 degrees C. Skin blood flow was measured continuously at two forearm skin sites, one with (UT) and without (BT) (treated with bretylium tosylate) intact alpha-adrenergic vasoconstrictor activity. The exercise threshold for cutaneous vasodilation in women (37.51 +/- 0.08 degrees C and 37.58 +/- 0.04 degrees C for UT and BT, respectively) was greater than that measured in men (37.33 +/- 0.06 degrees C and 37.35 +/- 0.06 degrees C for UT and BT, respectively) (P < 0.05). Core temperatures were similar to baseline before the start of whole body warming for all conditions. Postexercise heart rate (HR) for the men (77 +/- 4 beats/min) and women (87 +/- 6 beats/min) were elevated above baseline (61 +/- 3 and 68 +/- 4 beats/min for men and women, respectively), whereas mean arterial pressure (MAP) for the men (84 +/- 3 mmHg) and women (79 +/- 3 mmHg) was reduced from baseline (93 +/- 3 and 93 +/- 4 mmHg for men and women, respectively) (P < 0.05). A greater increase in HR and a greater decrease in the MAP postexercise were noted in women (P < 0.05). No differences in core temperature, HR, and MAP were measured in the no-exercise trial. The postexercise threshold for cutaneous vasodilation measured at the UT and BT sites for men (37.15 +/- 0.03 degrees C and 37.16 +/- 0.04 degrees C, respectively) and women (37.36 +/- 0.05 degrees C and 37.42 +/- 0.03 degrees C, respectively) were elevated above no exercise (36.94 +/- 0.07 degrees C and 36.97 +/- 0.05 degrees C for men and 36.99 +/- 0.09 degrees C and 37.03 +/- 0.11 degrees C for women for the UT and BT sites, respectively) (P < 0.05). A difference in the magnitude of the thresholds was measured between women and men (P < 0.05). We conclude that women have a greater postexercise onset threshold for cutaneous vasodilation than do men and that the primary mechanism influencing the difference between men and women in postexercise skin blood flow is likely the result of an altered active vasodilatory response and not an increase in adrenergic vasoconstrictor tone.     

Regional lung density and blood volume in nonsmoking and smoking subjects measured by PET

Regional lung density (DL) and regional fractional pulmonary blood volume (VB) were measured quantitatively during tidal breathing in 30 healthy supine subjects (15 smokers and 15 nonsmokers) in a 1.7-cm-thick midthoracic cross section using positron emission tomography (PET) and 11CO (inhaled)-labeled erythrocytes. Regional alveolar volume (VA), extravascular lung density (DEV), and relative alveolar size (Valv = VA/DEV) were calculated. For the nonsmokers, mean values (+/- SD between subjects) for the right lung were as follows: DL, 0.28 +/- 0.03 g/cm3; DEV, 0.10 +/- 0.02 g/cm3; and Valv, 7.1 +/- 1.9 ml/g lung tissue. In the smoking subjects DEV (right plus left lung) was 16% higher. No significant difference in VB between smokers and nonsmokers was found. The differences in DEV and VB between right and left lung were not significant. Mean values (+/- SD) of the dorsal-to-ventral ratios calculated for the right lung in the nonsmokers were as follows: DL, 1.34 +/- 0.16; VA, 0.90 +/- 0.05; VB, 1.52 +/- 0.26; DEV, 1.10 +/- 0.17; and Valv, 0.85 +/- 0.19. Almost identical ratios were found in the smokers. The influence of overall thoracic expansion was investigated in one subject restudied during voluntary hyperinflation and during positive end-expiratory pressure.     

Gender disparities in the association between epicardial adipose tissue volume and coronary atherosclerosis: A 3-dimensional cardiac computed tomography imaging study in Japanese subjects

ABSTRACT: BACKGROUND: Growing evidence suggests that epicardial adipose tissue (EAT) may contribute to the development of coronary artery disease (CAD). In this study, we explored gender disparities in EAT volume (EATV) and its impact on coronary atherosclerosis. METHODS: The study population consisted of 90 consecutive subjects (age: 63 +/- 12 years; men: 47, women: 43) who underwent 256-slice multi-detector computed tomography (MDCT) coronary angiography. EATV was measured as the sum of cross-sectional epicardial fat area on CT images, from the lower surface of the left pulmonary artery origin to the apex. Subjects were segregated into the CAD group (coronary luminal narrowing > 50%) and non-CAD group. RESULTS: EATV/body surface area (BSA) was higher among men in the CAD group than in the non-CAD group (62 +/- 13 vs. 33 +/- 10 cm3/m2, p < 0.0001), but did not differ significantly among women in the 2 groups (49 +/- 18 vs. 42 +/- 9 cm3/m2, not significant). Multivariate logistic analysis showed that EATV/BSA was the single predictor for >50% coronary luminal narrowing in men (p < 0.0001). Predictors excluded were age, body mass index, hypertension, diabetes mellitus, and hyperlipidemia. CONCLUSIONS: Increased EATV is strongly associated with coronary atherosclerosis in men.     

Sex and limb-specific ischemic reperfusion and vascular reactivity

With little known regarding sex and limb heterogeneity, we investigated vascular reactivity and ischemic reperfusion (IR) in the upper and lower extremities of 15 healthy men (26 +/- 2 yr) and women (23 +/- 1 yr). Doppler ultrasound was used to evaluate IR and flow-mediated dilation (FMD) after suprasystolic cuff occlusion in both the arm [brachial artery (BA)] and the leg [popliteal artery (PA)]. Cumulative IR [area under the curve (AUC)], normalized for muscle mass, revealed no sex-related differences in either limb (forearm: men 38 +/- 3 and women 44 +/- 4 ml/100 g; lower leg: men 12 +/- 2 and women 14 +/- 2 ml/100 g), while both groups revealed a greater IR per unit of arm muscle mass (AUC) compared with the lower leg (P < 0.05). The BA and PA were smaller in women (BA 0.31 +/- 0.1, PA 0.47 +/- 0.1 cm) than in men (BA 0.41 +/- 0.1, PA 0.6 +/- 0.2 cm). Absolute FMD/shear rate revealed attenuated vascular function in the PA of the women [women 3.3 +/- 0.6, men 5.0 +/- 0.8 (all x10(-6)) cm/s(-1).s] and no sex difference in the BA [women 1.2 +/- 0.2, men 1.6 +/- 0.1 (all x10(-6)) cm/s(-1).s]. In both sexes the PA demonstrated greater vascular reactivity than the BA. Thus vascular reactivity in healthy young people is greater in the legs, regardless of sex, and women have vascular function similar to men in the upper extremities but appear to have poorer vascular function normalized for shear rate in the lower extremities.     

Basal muscle intracellular amino acid kinetics in women and men

Sexual dimorphism in skeletal muscle mass is apparent, with men having more muscle mass and larger individual muscle cells. However, no sex-based differences have been detected in blood forearm phenylalanine turnover, although whole body leucine oxidation has been reported to be greater in men than in women. We hypothesized that sex differences in intracellular amino acid turnover may account for these discrepancies, with men having a higher intracellular turnover than women. We studied young, healthy women (women, n = 8) and men (men, n = 10) following an overnight fast. Phenylalanine, leucine, and alanine muscle intracellular kinetics were assessed using stable isotope methodologies, femoral arteriovenous blood sampling, and muscle biopsies. Muscle intracellular amino acid kinetics were reported relative to both leg volume and lean leg mass because of sex differences in leg volume and in muscle and fat distribution. When expressed per leg volume (nmol.min(-1).100 ml leg volume(-1)), phenylalanine net balance (women: -16 +/- 4, men: -31 +/- 5), release from proteolysis in the blood (women: 46 +/- 9, men: 75 +/- 10) and intracellular availability (women: 149 +/- 23, men: 241 +/- 35), and alanine production, utilization, and intracellular availability were higher in men (P < 0.05). However, when the kinetic parameters were normalized per unit of lean leg mass, all differences disappeared. Muscle fractional synthetic rate was also not different between women and men. We conclude that there are no sex-based differences in basal muscle intracellular amino acid turnover when the data are normalized by lean mass. It remains to be determined if there are sex differences in intracellular amino acid metabolism following anabolic or catabolic stimuli.     

Forebrain neural patterns associated with sex differences in autonomic and cardiovascular function during baroreceptor unloading

Generally, women demonstrate smaller autonomic and cardiovascular reactions to stress, compared with men. The mechanism of this sex-dependent difference is unknown, although reduced baroreflex sensitivity may be involved. Recently, we identified a cortical network associated with autonomic cardiovascular responses to baroreceptor unloading in men. The current investigation examined whether differences in the neural activity patterns within this network were related to sex-related physiological responses to lower body negative pressure (LBNP, 5, 15, and 35 mmHg). Forebrain activity in healthy men and women (n = 8 each) was measured using functional magnetic resonance imaging with blood oxygen level-dependent (BOLD) contrast. Stroke volume (SV), heart rate (HR), and muscle sympathetic nerve activity (MSNA) were collected on a separate day. Men had larger decreases in SV than women (P < 0.01) during 35 mmHg LBNP only. At 35 mmHg LBNP, HR increased more in males then females (9 +/- 1 beats/min vs. 4 +/- 1 beats/min, P < 0.05). Compared with women, increases in total MSNA were similar at 15 mmHg LBNP but greater during 35 mmHg LBNP in men [1,067 +/- 123 vs. 658 +/- 103 arbitrary units (au), P < 0.05]. BOLD signal changes (P < 0.005, uncorrected) were identified within discrete forebrain regions associated with these sex-specific HR and MSNA responses. Men had larger increases in BOLD signal within the right insula and dorsal anterior cingulate cortex than women. Furthermore, men demonstrated greater BOLD signal reductions in the right amygdala, left insula, ventral anterior cingulate, and ventral medial prefrontal cortex vs. women. The greater changes in forebrain activity in men vs. women may have contributed to the elevated HR and sympathetic responses observed in men during 35 mmHg LBNP.     

Volume and compressibility changes accompanying thermally-induced native-to-unfolded and molten globule-to-unfolded transitions of cytochrome c: a high pressure study

We have measured the transition temperatures, T(M), and van't Hoff enthalpies, DeltaH(M), of the thermally induced native-to-unfolded (N-to-U) and molten globule-to-unfolded (MG-to-U) transitions of cytochrome c at pressures between 50 and 2200 bar. We have used the pressure dependence of T(M) to evaluate the changes in volume, Delta(v), accompanying each protein transition event as a function of temperature and pressure. From analysis of the temperature and pressure dependences of Delta(v), we have additionally calculated the changes in expansibility, Delta(e), and isothermal compressibility, Delta(k)(T), associated with the thermally induced conformational transitions of cytochrome c. Specifically, if extrapolated to 25 degrees C, the native-to-unfolded (N-to-U) transition is accompanied by changes in volume, Delta(v), expansibility, Delta(e), and isothermal compressibility, Delta(k)(T), of -(5 +/- 3) x 10(-3) cm(3) g(-1), (1.8 +/- 0.3) x 10(-4) cm(3) g(-1) K(-1), and approximately 0 cm(3) g(-1) bar(-1), respectively. The molten globule-to-unfolded (MG-to-U) transition is accompanied by changes in volume, Delta(v), and isothermal compressibility, Delta(k)(T), of -(2.9 +/- 0.3) x 10(-3) cm(3) g(-1) at 40 degrees C and -(1.9 +/- 0.3) x 10(-6) cm(3) g(-1) bar(-1) at 35 degrees C, respectively. By comparing the volumetric properties of the N-to-U and N-to-MG transitions of cytochrome c, we have estimated the properties of the native-to-molten globule (N-to-MG) transition. For the latter transition, the changes in volume, Delta(v), and isothermal compressibility, Delta(k)(T), are approximately 0 cm(3) g(-1) at 40 degrees C and 1.9 cm(3) g(-1) bar(-1) at 35 degrees C, respectively. Our estimate for the change in expansibility, Delta(e), upon the N-to-MG is negative and equal to -(5 +/- 3) x 10(-4) cm(3) g(-1) K(-1). This finding contrasts with the results of previous studies all of which report positive changes in expansibility associated with protein denaturation. In general, our volumetric data permit us to assess the combined effect of temperature and pressure on the stability of various conformational states of cytochrome c.     

Formation of androstanediol from 13C-labeled testosterone in humans

The determination of urinary 5 alpha-androstane-3 alpha,17 beta-diol (3a-Diol) by gas chromatography/mass spectometry during and after the infusion of stable-labeled testosterone (T) represents an alternative to the use of radioactive label for turnover studies in vivo. Using this methodology to assess the urinary excretion rates of T and 3a-Diol in healthy men (n = 6) and women (n = 5) during and after the intravenous infusion (t = 4 hours) of 20 mg (men) or 5 mg (women) [13C]testosterone, the cumulative renal excretion of 13C-labeled T was found to be 15.6 +/- 9.6 micrograms/24 hours (men) and 1.1 +/- 1.6 micrograms/24 hours (women), equivalent to 0.08% +/- 0.05% and 0.02% +/- 0.03% of the infused amount of 13C-T, respectively. The cumulative excretion of 13C-3a-Diol was 67.7 +/- 19.9 micrograms/24 hours (men) and 10.0 +/- 6.0 micrograms/24 hours (women), equivalent to 0.3 +/- 0.1% and 0.2 +/- 0.1% of the infused dose of 13C-labeled testosterone, respectively.     

The quantitative relationship between longitudinal and radial function in left, right, and total heart pumping in humans

The total heart volume variation (THVV) during systole has been proposed to be caused by radial function of the ventricles, but definitive data for both ventricles have not been presented. Furthermore, the right ventricle (RV) has been suggested to have a greater longitudinal pumping component than the left ventricle (LV). Therefore, we aimed to compare the stroke volume (SV) generated by radial function to the volume variation of the left, right, and total heart. To do this, we also needed to develop a new method for measuring the contribution of the longitudinal atrioventricular plane displacement (AVPD) to the RVSV (RVSV(AVPD)). For our study, 11 volunteers underwent cine MRI in the short- and long-axis planes and MRI flow measurement in all vessels leading to and from the heart. The left, right, and total heart showed correlations between volume variation from flow measurements and radial function calculated as SV minus the longitudinal function (r = 0.81, P < 0.01; r = 0.80, P < 0.01; and r = 0.92, P < 0.001, respectively). Compared with the LV, the RV had a greater AVPD (23.4 +/- 0.8 vs. 16.4 +/- 0.5 mm), center of volume movement (13.0 +/- 0.7 vs. 7.8 +/- 0.4 mm), and, RVSV(AVPD) (82 +/- 2% vs. 60 +/- 2%) (P < 0.001 for all). We found that THVV is predominantly caused by radial function of the ventricles. Longitudinal AVPD accounts for approximately 80% of the RVSV, compared with approximately 60% for the LVSV. This difference explains the larger portion of THVV found on the left side of the heart.     

The benefits of regular kinesiotherapy once a week for postmenopausal women: an aged-matched study

Regular exercise training improves overall physical fitness and quality of life in postmenopausal women. The exigent training frequency depends on a user-specified training aim. The aim of this study was to confirm the benefits of regular once a week exercise training for the maintenance of fitness in postmenopausal women. The test group included 20 postmenopausal women (65 +/- 3.1 years) who have been attending the exercise training program conducted by the physiotherapist once a week for three years. The age-matched control group included 20 healthy women (65.5 +/- 2.4 years) who did not regularly attend the training program. The outcomes were: right and left lateral trunk flexion, right and left shoulder flexion, right and left grip strength, endurance capacity of the trunk extensors, lower limb muscle strength (1' chair stand test), and balance (one-leg standing duration time with eyes open and closed). Women from the test group achieved statistically significant better results in the following outcomes: right lateral trunk flexion (15.4 cm: 12.6 cm, p < 0.001), left lateral trunk flexion (15.4 cm: 12.6 cm, p = 0.001), trunk extension muscle endurance (53.4 s: 40.5 s, p < 0.001), lower limb muscle strength (28.4 x: 25 x, p < 0.001), and one-leg standing duration time with open eyes (33.5 s: 19.7 s, p < 0.001). The results suggest that a regular once a week exercise training program designed and conducted by the physiotherapist, may be helpful in the improvement or maintenance of flexibility, muscle strength and capacity, and balance in postmenopausal women. The better fitness proved by our study could be a result of other causes and not solely that of the designed training program.     

New bioimpedance model accurately predicts lower limb muscle volume: validation by magnetic resonance imaging

Conventional bioimpedance analysis (BIA) methods now simplify the representation of lower limb geometry and electrical properties for body composition estimation. In the present study, a three-dimensional model of the lower limb was assembled by segmentation of magnetic resonance cross-sectional images (MRI) for adipose tissue, skeletal muscle, and bone. An electrical network was then associated with this model. BIA and MRI measurements were made in six lean subjects (3 men and 3 women, age 32.2 +/- 6.9 yr). Assuming 0.85 S/m for the longitudinal conductivity of the muscle, the model predicted in the examined subjects an impedance profile that conformed well to the BIA impedance profile; predicted and measured resistances were similar (261.3 +/- 7.7 vs. 249 +/- 9 Omega; P = not significant). The resistance profile provided, through a simpler model, muscle area estimates along the lower limb and total leg muscle volume (mean 4,534 cm(3) for men and 4,071 cm(3) for women) with a mean of the absolute value of relative error with respect to MRI of 6.2 +/- 3.9. The new approach suggests that BIA can reasonably estimate the distribution and volume of muscles in the lower extremities of lean subjects.     

Breast volume assessment based on 3D surface geometry: verification of the method using MR imaging

Differences in breast volume and contour are subjectively estimated by surgeons. 3D surface imaging using 3D scanners provides objective breast volume quantification, but precision and accuracy of the method requires verification. Breast volumes of five test individuals were assessed using a 3D surface scanner. Magnetic resonance imaging (MRI) reference volumes were obtained to verify and compare the 3D scan measurements. The anatomical thorax wall curvature was segmented using MRI data and compared to the interpolated curvature of the posterior breast volume delimitation of 3D scan data. MRI showed higher measurement precision, mean deviation (expressed as percentage of volume) of 1.10+/-0.34% compared to 1.63+/-0.53% for the 3D scanner. Mean MRI [right (left) breasts: 638 (629)+/-143 (138) cc] and 3D scan [right (left) breasts: 493 (497)+/-112 (116) cc] breast volumes significantly correlated [right (left) breasts: r=0.982 (0.977), p=0.003 (0.004)]. The posterior thorax wall of the 3D scan model showed high agreement with the MRI thorax wall curvature [mean positive (negative) deviation: 0.33 (-0.17)+/-0.37 cm]. High correspondence and correlation of 3D scan data with MRI-based verifications support 3D surface imaging as sufficiently precise and accurate for breast volume measurements.     

多层螺旋CT测量成年贵州小型猪活体肾参考数据

目的通过测量成年贵州小型猪肾脏各种径线值及体积,建立贵州小型猪肾脏数据。方法采用西门子双源CT对12头成年贵州小型猪(雄性6头,雌性6头)进行薄层容积扫描,原始数据经Aquarius iNtuition4.4软件进行MRP及VR重组,在横断位正中层面测量双肾前后径及左右径,在冠状位最大面测量双肾长径及短径,计算小型猪体积及双肾体积,双肾长径与短径比值,采用统计学软件对肾长径、长短径比值与肾脏体积,肾脏体积与小型猪体积及体重做相关性分析,P0.05为差异有统计学意义。结果左肾前后径及左右径分别为(40.40±1.67)mm及(27.47±1.40)mm,长径及短径分别为(80.36±2.74)mm及(31.79±1.99)mm,左肾体积为(52.78±2.25)cm3,左肾长径与短径比值为(2.42~2.71)∶1;右肾前后径及左右径分别为(40.95±1.43)mm及(26.90±0.65)mm,长径及短径分别为(79.03±2.38)mm及(32.04±2.34)mm,右肾体积为(51.91±2.25)cm3,右肾长径与短径比值为(2.33~2.77)∶1。双肾长径与肾脏体积呈高度正相关(r左=0.92,P0.05;r右=0.88,P0.05),肾脏体积与小型猪体积呈正相关(r左=0.90,P0.05;r右=0.81,P0.05),与体重也呈高度正相关(r左=0.96,P0.05;r右=0.98,P0.05),但肾脏长短径比值与体积呈负相关(r左=-0.51,P0.05;r右=-0.67,P0.05)。结论多层螺旋CT及其后处理软件可准确测量贵州小型猪活体肾脏的多项影像学数据,为人类肾脏疾病的动物模型研究提供参考。     

Staphylococci in skin microbiocenosis of the breasts in healthy women

The autoflora of different anatomical regions of the mammary glands in 120 healthy nulliparous women aged 18-24 years was studied by P. Williamson and A. M. Kligler's methods of smears and washings. From the nipple, the areola, and the adjacent region of the skin 2,248 strains of anaerobic microorganisms were isolated; of these, 63.83% were staphylococci and micrococci, 6.01% were streptococci, 1.91% were Neisseria, 17.79% were Corynebacterium, 3.87% were bacilli, 2.8% were enterobacteria, and 3.79% were fungi. Coagulase-positive staphylococci occurred in 1.56% of cases. Out of 11 coagulase-negative species of this genus, S. epidermidis occurred most frequently on the skin of the mammary glands. The nipple was found to have the highest bacterial contamination (0.55 X 10(6) +/- 0.7 X 10(5) cells/sq. cm for the right mamma and 0.59 X 10(6) +/- 0.7 X 10(5) cells/sq. cm for the left mamma) and the skin adjacent the areola, the lowest bacterial contamination (0.14 X 10(4) +/- 0.2 X 10(3) cells/sq. cm for the right mamma and 0.25 X 10(4) +/- 0.3 X 10(3) cells/sq. cm for the left mamma). P. Williams and A. M. Kligman's method of washings, more accurate and informative, was found to be preferable for the study of the quantitative characteristics of the dermal microbiocenosis of the mammary glands.     

Site-specific in vivo targeting of magnetoliposomes using externally applied magnetic field

Human serum albumin labeled with technetium-99m was encapsulated together with magnetite particles into phosphatidylcholine/cholesterol liposomes. In order to investigate the stability of this complex and its ability to be used for magnetic drug targeting, the in-vivo distribution after intravenous administration in rats was estimated. For in-vivo targeting an SmCo permanent magnet with intensity approximately 0.35 T was attached near the right kidney. Difference between the relative radioactivity in the magnetically targeted right kidney (25.92+/-5.84%) and non-targeted left kidney (0.93+/-0.05%) is sufficiently high for relevant clinical applications.     

Sprint training attenuates the deficits of force and dynamic stiffness in rat soleus muscle caused by eccentric contractions

We investigated whether sprint training attenuates the deficits in force and dynamic stiffness caused by eccentric contractions to the soleus muscles of Wistar rats. Two groups of male rats were analyzed: sedentary (C, n=8) and trained (T, n=8). T rats were sprint trained for 10 weeks. Subsequently, the right soleus muscles of rats were freed under anesthesia, leaving the bone insertion and blood supply intact. Eccentric contractions were induced by lengthening muscles during tetanic contractions. Force and dynamic stiffness were tested before and after 20 rounds of eccentric contractions. Tension decline was analyzed using a two-state model (first-order kinetics) in the context of Kramer's theory. Training improved the twitch tension (C, 6.44+/-0.6N/cm(2); T, 10.90+/-0.8N/cm(2)), tetanic force (C, 61.74+/-0.6N/cm(2); T, 85.62+/-0.8N/cm(2)), and increased the dynamic stiffness (C, 41.28+/-1.0N/cm(2); T, 49.56+/-3.2N/cm(2)). Twitch tension after eccentric contractions declined to 73% and 75% in C and T groups, respectively, while tetanic tension decreased to 60% and 36% in C and T groups, respectively. After eccentric contractions, dynamic stiffness decreases were smaller in T rats (from 49.56+/-3.2 to 36.09+/-2.1N/cm(2)) than in C rats (from 41.28+/-1.0 to 20.73+/-1.8N/cm(2)). Sprint training increased the dynamic stiffness and tetanic tension of the soleus muscle and protected against the attenuation induced by eccentric contractions. Finally, the two-state model provided evidence that the number of force-generating cross-bridges increases in trained muscle.     

The effects of clonidine on the kidney function in the anesthetized dog

Studies were performed to determine the mechanism by which the antihypertensive agent clonidine increased urine flow. The response of the kidney has been examined in four combinations. The parameters of renal function have been compared during volume expansion by 1.5-2.0% body weight Ringer solution. In the control animals, volume expansion by 2% body weight, resulted in a slight increase in sodium excretion and urine flow. In 10 anesthetized dogs 1.0 microgram/kg/min of clonidine infused i.v. during 30 minutes (the total amount of clonidine infused was 30 micrograms/kg) decreased the arterial blood pressure from 136 +/- 13 mmHg to 127 +/- 12 mmHg and elevated urine flow from 2.95 +/- 1.65 ml/min to 4.34 +/- 1.77 ml/min while the urine osmolality diminished from 399 +/- 107 mosm/l to 265 +/- 90 mosm/l and the glomerular filtration remained constant. In 5 animals 0.1 microgram/kg/min of clonidine was infused into the left renal artery (this dose is corresponding to the renal fraction of the cardiac output) without any effects in the left kidney. 1.0 microgram/kg/min of clonidine infused directly into the left renal artery produced vasoconstriction in the ipsilateral kidney, decreased the glomerular filtration rate and the urine flow. By contrast in the right kidney the urine flow rose without hemodynamic changes, and the urine osmolality became hypoosmotic compared to the plasma. In ten dogs 1.0 microgram/kg/min of clonidine and 1 mU/kg/min of arginine-vasopressin were infused intravenously. The vasopressin infusion superimposed on the clonidine could not inhibit the increase of the urine excretion, and the fall of the urine osmolality. The results suggest that the clonidine increases the renal medullary blood flow possibly via a direct mechanism, decreases the sympathetic outflow to the kidney and via an indirect pathway, mediated by the renin-angiotensin system. The renal medullary flow increase produces a washout of the medullary osmotic gradient, and the water reabsorption diminishes.     

Comparison of thermoregulatory responses between men and women immersed in cold water.

Eleven women (age = 24.4 +/- 6.3 yr, mass = 65.0 +/- 7.8 kg, height = 167 +/- 8 cm, body fatness = 22.4 +/- 5.9%, mean +/- SD) were immersed to neck level in 18 degrees C water for up to 90 min for comparison of their thermal responses with those of men (n = 14) in a previous similarly conducted protocol. Metabolic rate increased about three times resting levels in men and women, whereas the rate of rectal temperature cooling (DeltaT(re)/Deltat) in women (0.47 degrees C/h) was about one-half that in men. With use of all data, DeltaT(re)/Deltat correlates with the ratio of body surface area to size and the metabolic rate of shivering correlates inversely to the square root of body fatness. No significant gender differences in total metabolic heat production normalized for body mass or surface area were found among subjects who completed 90 min of immersion (9 women and 7 men). Nor was there a gender difference in the overall percent contribution ( approximately 60%) of fat oxidation to total heat production. Blood concentrations of free fatty acids, glycerol, beta-hydroxybutyrate, and lactate increased significantly during the 90-min immersion, whereas muscle glycogen sampled from the right quadriceps femoris vastus lateralis decreased (free fatty acids, glycerol, and beta-hydroxybutyrate were higher in women). When the subjects were subgrouped according to similar body fatness and 60 min of immersion (6 women and 5 men), no significant gender differences emerged in DeltaT(re)/Deltat, energy metabolism, and percent fat oxidation. These findings suggest that no gender adjustments are necessary for prediction models of cold response if body fatness and the ratio of body surface area to size are taken into account and that a potential gender advantage with regard to carbohydrate sparing during cold water immersion is not supported.     

Sizes and concentrations of several type C oncornaviruses and bacteriophage T2 by the resistive-pulse technique.

Viruses above about 60 nm in diameter may be rapidly sized to a few nanometers in their natural hydrated state as they pass one by one through a single pore in a newly developed nanometer-particle analyzer based on the resistive-pulse technique of the Coulter Counter and the use of submicron diameter pores made by the Nuclepore process. Size measurements for several type C oncornaviruses are: Rauscher murine leukemia, 122.3 +/- 2 nm; simian sarcoma, 109.7 +/- 3 nm; Mason-Pfizer monkey, 140.0 +/- 2.5 nm; RD-114, 115 +/- 5 nm; and feline leukemia, 127.4 +/- 2 nm, relative to standard 109-nm latex spheres. The T2 bacteriophage has a volume of (5.10 +/- 0.15) X 10(-16) cm3. Concentrations of viruses near 10(9) to 10(11)/ml that are fairly clear of debris are routinely measurable in a few minutes to an accuracy near 15%. A lower practical count limit is near 5 X 10(7) viruses per ml.     

Effect of gender on vestibular sympathoexcitation

Studies have suggested that premenopausal women are more prone to orthostatic intolerance than men. Additionally, it has been postulated that the vestibulosympathetic reflex is important in regulating postural-related changes in sympathetic activity. The purpose of the present study was to determine whether men and women differ in their sympathetic and cardiovascular responses to stimulation of the otolith organs elicited by head-down rotation (HDR). Heart rate (HR), arterial pressure, calf blood flow (CBF), and leg muscle sympathetic nerve activity (MSNA) were measured during 3 min of HDR in the prone posture in 33 women and 30 men. With the exception of HR (71 +/- 2 and 63 +/- 1 beats/min for women and men, respectively; P < 0.01), all baseline variables were not different between genders. There were no gender differences in responses to HDR. MSNA increased 72 +/- 33 units (43%) in the men and 88 +/- 15 units (59%) in the women during HDR (P < 0.01). CBF decreased [-0.6 +/- 0.1 (15%) and -0.5 +/- 0.1 (19%) ml. min(-1). 100 ml(-1)] and calf vascular resistance increased [8 +/- 2 (21%) and 11 +/- 3 (25%) units during HDR for men and women, respectively (P < 0.01)]. Both in the men and women, HR increased 2 +/- 1 beats/min (P < 0.01). These results demonstrate that sympathetic activation during HDR in the prone posture is similar in men and women. Therefore, these findings suggest that the vestibulosympathetic reflex is not different between healthy men and women.